1. Field of the Invention
This invention relates to fluid bearings and more particularly to a spherical fluid bearing apparatus for freely supporting a device on an apparatus support surface.
2. Description of the Related Art
Ground testing of space flight vehicles is generally limited to three options. A first option is suborbital hot fire flight testing. The second option is the use of computer simulated models for testing flight dynamics. A third option is the use of a spherical air bearings mounted at the center of the vehicle's center of mass.
Hot fire testing is very expensive and typically results in the consumption of the flight vehicle. Computer simulated modeling may not be entirely effective because the hardware itself is not tested. The third option, involving use of an air bearing at the center of mass of the vehicle, requires removing essential parts of the vehicle that are currently located at the vehicle's center of mass.
U.S. Pat. No. 3,135,057, issued to G. A. Nelson et al., entitled "Flight Simulator", discloses a spherical shell-like device adapted to subject a human being to rotation flight control problems which may be encountered in space flight. The simulator consists of a hollow sphere mounted on an air-bearing pedestal or the like for rotation about three axes having a normal relation with respect to each other.
Nelson's requirement of encompassing the test device (i.e. in his case a human subject) in a hollow sphere results in a substantial weight change to the device. Furthermore, utilization of a sphere as part of the test simulator prevents use of any thrusters during testing which may be located on the outer surface of the test device. For the above reasons, the Nelson device provides diminished results.
U.S. Pat. No. 2,695,199, issued to R. B. Blizard, entitled "Bearing", discloses a bearing for freely supporting a sensitive element. The bearing comprises a cup, a spherical surface on the sensitive element resting in the cup, means for introducing lubricant between the spherical surface and the cup and points above the bottom and below the top of the cup, and means for withdrawing lubricant from the bottom of the cup.
The bearing disclosed by Blizard would not be effective as a bearing for use in testing flight vehicles because the center of mass of the sensitive element in that case is not disposed coincident with the spherical surface center of rotation.
Accurate simulation of flight vehicles requires center of rotation to occur at the center of mass of the flight vehicle. Currently, such a disposition has been achieved by hot fire testing or use of the spherical bearing at the center of the flight vehicle. The prior art does not allow for free rotation of an assembled flight vehicle device without replacing parts at the center of mass of the device with a spherical bearing or by adding substantial weight to the device.